The use of optical indicia, such as bar code symbols, for product and article identification is well known in the art. Presently, various types of indicia reading terminals have been developed, such as hand-held bar code scanners, hands-free scanners, bi-optic in-counter scanners, and mobile computers such as personal digital assistants (PDAs).
One common type of scan engine found in hand-held and retail scanners is the laser-based scan engine, which uses a focused laser beam to sequentially scan the bars and spaces of a bar code symbol pattern to be read. As the laser beam is scanned across the bar code symbol, a portion of the reflected light beam is collected by optics within the scanner. The collected light signal can subsequently be focused upon a photo-detector within the scanner. The photo-detector can, in one example, generate an analog electrical signal which can be converted into a digital signal representative of the bar code symbol.
Another common type of indicia reading terminal is the digital imager, which includes 1D (linear) imagers and 2D (area) imagers. Digital imagers typically utilize light emitting diodes (LEDs) and a lens to focus the image of the bar code onto a multiple pixel image sensor, which is often provided by a complementary metal-oxide semiconductor (CMOS) image sensor that converts light signals into electric signals. The LEDs simultaneously illuminate all of the bars and spaces of a bar code symbol with light of a specific wavelength in order to capture an image for recognition and decoding purposes.